Method for controlling pressure in a hydraulic circuit

ABSTRACT

The invention is based on an apparatus ( 10 ) for regulating the pressure in a hydraulic circuit that comprises an electrically triggerable pressure-control valve ( 12 ), a receptacle device ( 14 ) in which the pressure-control valve ( 12 ) is installed, and means ( 54, 64 ) for damping pressure pulsations. In order to save space, simplify the manufacture of the receptacle device ( 14 ), and save additional holding elements, it is proposed according to the invention that the means ( 54, 64 ) for damping pressure pulsations be designed as integral components of the pressure-control valve ( 12 ).

BACKGROUND OF THE INVENTION

The invention is based on an apparatus for regulating the pressure in ahydraulic circuit. Apparatuses of this type are used in automaticgearboxes of motor vehicles in particular, to trigger gear changes viacontrol of the pressure level, for example.

For this, known apparatuses comprise an electrically triggerablepressure-control valve, like the one made known previously in DE 197 33660 A, for example. This pressure-control valve comprises a solenoidpart constructed in conventional fashion having coil, coil core, fluxconcentrating element and armature, and a hydraulic part havingmechanical linkage with the solenoid part. In the hydraulic part, ashutoff element able to be acted upon by the armature controls the flowof hydraulic fluid between inlet passages, working passages, and returnpassages.

This known pressure-control valve can be installed with its hydraulicpart in a receptacle device—a “hydraulic control block”—in whichrecesses are provided that direct hydraulic fluid and are matched to thecorresponding passages of the pressure-control valve. Appropriatedevices are provided to dampen pressure pulsations, which can occurduring operation of the pressure-control valve in the recess matched tothe working passage. These devices are attached in the receptacle deviceas separate components.

The separate arrangement of the damping devices described isdisadvantageous, because it makes a large number of holding elementsnecessary, takes up a relatively large space, generates additional work,and is costly to install.

SUMMARY OF THE INVENTION

In contrast, an apparatus according to the invention for controlling thepressure in a hydraulic circuit has the advantage that the means fordamping pressure pulsations are an integral component of thepressure-control valve. This saves space, simplies the manufacture ofthe receptacle device, and makes separate holding elements superfluous,without making assembly of the pressure-control valve itself moredifficult. The pressure pulsations are damped by means of the inventiondirectly at the site of origin, which greatly improves the dampingeffect. Due to the damping, the pressure/flow characteristic of apressure-control valve can be kept within narrow tolerances under nearlyall operating conditions. Additionally, the prevention of pressurepulsations has a positive effect on the wearing behavior of thepressure-control valve, so that its service life is extended.

The devices can be integrally molded on one of the sealing elements ofthe pressure-control valve particularly easily, so that the total numberof components to be obstructed remains unchanged. The devices, togetherwith the housing of the pressure-control valve, enclose a dampingchamber having a variable volume. Its damping behavior can be varied bymeans of vents to the recess of the receptacle device matched to thereturn passage of the pressure-control valve in accordance with thespecific case of application. This vent can also be designed inadvantageous fashion as throttling point.

BRIEF DESCRIPTION OF THE DRAWING

Exemplary embodiments of the invention are presented in the drawing andexplained in greater detail in the following description.

FIGS. 1 and 2 are sectional diagrams of a longitudinal section of twodifferent exemplary embodiments of an apparatus according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Each of the apparatuses for controlling the pressure in a hydrauliccircuit labelled in FIGS. 1 and 2 with the position number 10 comprisesan electronically triggerable pressure-control valve 12 and a receptacledevice 14 in which this pressure-control valve 12 with its hydraulicpart 18 is installed. In addition to its hydraulic part 18, thepressure-control valve 12 also comprises a solenoid part 16. Comprisingthis solenoid part 16, an electrically triggerable, hollow-cylindricalcoil 20, a moveably guided armature 22, and a flux concentrating element24 surrounding the coil on its circumference are shown in sections.

The armature 22 comprises a section 22 a projecting into the interior ofthe coil 20, a collar 22 b adjoining this and spanning the front side ofthe coil 20, and a neck 22 c in axial extension of this collar 22 b. Athrough hole 26 extends through the center of the armature 22, intowhich a pushrod 28 is pressed in the region of the neck 22 c. Thispushrod 28 penetrates a guide 30 provided in the hydraulic part 18 anddesigned in the shape of an eyelet and actuates a shutoff element 32with its end, the outer diameter of which is tapered. The shutoffelement 32 is designed in the shape of a ball and bears against thepushrod 28 as a result of hydraulically-induced forces of flow andpressure. The shutoff element 32 serves to control a first valve seat 34formed in the hydraulic part 18, the inner diameter of which is greaterthan the outer diameter of the pushrod 28. An annular orifice thereforeexists between pushrod 28 and valve seat 34, through which hydraulicfluid can flow when the valve seat 34 is opened.

A second valve seat 36 of the hydraulic part 18 is formed on aperforated plate 38 that is injected, facing the solenoid part 16, intothe hydraulic part 18. This perforated plate 38 is controlled by thefront end of the neck 22 c and lies in alignment with the first valveseat 34. In the non-energized starting position of the armature 22shown, the first valve seat 34 is open and the second valve seat 36 isclosed. In addition, the armature 22 is moved into the starting positionshown by a return device, e.g., in the form of a spring (not shown).Current is not supplied to the coil 20.

The hydraulic part 18 is firmly connected to the solenoid part 16 of thepressure-control valve 12. This solenoid part 16 is manufactured usinginjection molding technology, preferably using plastic, and comprises aninjected holding element 40. The latter is designed in the shape of asleeve, and its diameter is offset repeatedly. A non-extrusion-coatedpart of the holding element 40 projects over the hydraulic part 18 andfirmly encloses the flux concentrating element 24 of the solenoid part16. A second guide 42 for the armature 22 is located at the smallestdiameter of the holding element 40 lying inside the hydraulic part 18.At the same time, this guide 42 forms an end stop for limiting theup-and-down motion of the armature 22.

A continuous, longitudinal recess 44 extending in the direction of itslongitudinal axis is provided at the hydraulic part 18 for directinghydraulic fluid, into which two transverse passages 46, 48, oneextending over the top of the other, empty at right angles. The firsttransverse passage 46 facing the solenoid part 16 is designed in thefashion of a blind hole and forms the return passage R of thepressure-control valve 12, while the transverse passage 48 opposite tothe solenoid part 16 penetrates the hydraulic part 18 and acts as theworking passage A. The front end of the longitudinal recess 44 forms aninlet passage 50—labelled “P”—for the hydraulic part 18. The latterempties into the working passage A when the valve seat 34 is open, whilethe hydraulic passage between the working passage A and the returnpassage R is interrupted. Using an electrically triggered coil 20, theserelationships are reversed accordingly, that is, a hydraulic connectionexists between the return passage R and the working passage A, while theinlet passage P is blocked.

Recesses 46′, 48′, 50′ of the receptacle device 14 are matched to thepassages 46, 48, 50 of the pressure-control valve 12. Sealing elements52 and 54 are provided on the circumference of the hydraulic part 18 forthe mutual sealing of these recesses 46′, 48′, 50′. The first sealingelement 52 separating the inlet passage P from the working passage A isa conventional O-ring that is held on a filter cage 56. The annularfilter cage 46 manufactured out of plastic that is resistant tohydraulic fluid is slid onto the end section of the hydraulic part 18and comprises a filter fabric that covers the opening cross section ofthe working passage A. This filters contaminants out of the hydraulicfluid flowing out of the working passage A to a hydraulic consumingdevice (not shown).

The second sealing element 54 serving to separate the working pasage Afrom the return passage R is composed, according to the invention, of anO-ring cross section 58 having sealing function and an integrally moldeddiaphragm 60 having a thickened end 62. The sealing element 54 is alsoproduced out of elastic material resistant to hydraulic fluid havinggood impermeability properties, so that the diaphragm 60 can bestretched using its thickened end 62 between the filter cage 56 and ashoulder of the hydraulic part 18 on the housing side. An annularpressure chamber 64 closed off from the surroundings is thereby producedbetween the diaphragm 60 and the housing of the hydraulic part 18. Theinterior space of this pressure chamber 64 is filled with air.

In the installed stated of the pressure-control valve 12 shown, thediaphragm 60 is located in the recess 48′ of the receptacle device 14matched to the working passage A. Due to its malleability and,therefore, the variability of the volume of the pressure chamber 64enclosed by it, the latter is capable of damping pressure pulsationsthat can occur in the working passage 48 and the connected recess 48′.Using the sealing element 54 designed according to the invention,therefore, a hydraulic capacity is created in the working passage Awithout appreciably changing the space required therefore, the number ofindividual parts or the installation expenditure required. An increasein the stiffness of the diaphragm 60 could be realized, if necessary, bymeans of a spring element (not shown) that can be located in theinterior space of the pressure chamber 64. By varying the springelements used, a damping characteristic adapted to the specific case ofapplication could be achieved.

The second exemplary embodiment according to FIG. 1 differs from thefirst exemplary embodiment by the fact that the pressure chamber 60—thevolume of which can be changed—is connected to the recess 46′ of thereceptacle device 14 matched to the return passage R of thepressure-control valve 12 via a vent 66. As a further actuating variableon the damping characteristic, the vent 66 can be designed as dampingthrottle. It would also be feasible to provide a plurality of such vents66 or to divide the pressure chamber 64 into multiple sections.

Further-reaching changes or additions to the exemplary embodiments arepossible, of course, without deviating from the basic idea of theinvention. A 3/2 directional-control proportioning valve is preferablyused as the pressure-control valve 12, the armature 22 of which can bemoved into any intermediate position by the solenoid part 16. Operatingpositions can also be described in which both valve seats 34 and 36 areopen simultaneously.

What is claimed is:
 1. An apparatus (10) for regulating the pressure ina hydraulic circuit having an electrically triggerable pressure-controlvalve (12) that comprises a solenoid part (16) having an electricallytriggerable coil (20), a moveably guided armature (22) and a hydraulicpart (18) coupled to the solenoid part (16), in which a shutoff element(32) able to be acted upon by the armature (22) controls the flow ofhydraulic fluid between at least one working passage (48) and a returnpassage (46), and having means (54, 64) for damping pressure pulsationsin the working passage (48), wherein the means (54, 64) are an integralcomponent of the pressure-control valve (12) and, in interaction withits housing, limit at least one pressure chamber (64) located on thecircumference and having a variable volume.
 2. The apparatus accordingto claim 1, wherein at least one wall of the pressure chamber (64) isformed by an elastically malleable diaphragm (60).
 3. The apparatusaccording to claim 2, wherein the diaphragm (60) is integrally molded ona sealing element (54) of the pressure-control valve (12).
 4. Theapparatus according to claim 3, wherein the end of the diaphragm (60)located at a distance from the sealing element (54) is fixable withaxial separation from this sealing element (54) on the circumference ofthe pressure-control valve (12).
 5. The apparatus according to claim 3,wherein the sealing element (54) forming the diaphragm (60) seals offthe return passage (46) and the working passage (48) from each other. 6.The apparatus according to claim 1, wherein the pressure chamber (64) ishermetically sealed off from the surroundings.
 7. The apparatusaccording to claim 1, wherein the pressure chamber (64) is connected tothe return passage (46) by means of a vent (66).
 8. The apparatusaccording to claim 7, wherein the vent (66) is outfitted with a dampingthrottle.
 9. The apparatus according to claim 1, wherein thepressure-control valve (12) is designed as a hydraulic 3/2directional-control proportioning valve that comprises an inlet passage(50) in addition to the working passage (48) and the return passage(46).
 10. A control device for an automatic gearbox of a motor vehiclehaving an apparatus (10) according to claim 1.